Differential expression of zebrafish gpia and gpib during development.

Glucose 6-phosphate isomerase (GPI), alternatively named phosphoglucose isomerase (PGI), autocrine motility factor (AMF) or neuroleukin (NLK), is a sugar metabolic enzyme catalyzing the interconversion between glucose-6-phosphate and fructose-6-phosphate. When secreted out of the cell, it can induce cellular activities of neighboring cells. As a prerequisite to study the function of gpi during development, we analyzed the sequences and expression patterns of zebrafish gpia and gpib. Phylogenetic analyses indicate that gpia and gpib are two paralogs resulting from the teleost fish-specific whole genome duplication. In adult zebrafish, gpia is widely expressed in many tissues, whereas gpib is only expressed in heart, muscle, and at lower abundance in eye. During embryonic development, gpia mRNA is maternally deposited in cleavage and blastula embryos, but gpib mRNA is not. Zygotic expression of gpia mRNA initiates in the primitive gut of segmentation embryos, and its expression increases in eye, cerebellum, hindbrain, heart, pharyngeal arches, pectoral fin buds and gut of hatching embryos at 60hpf (hours post fertilization). At 72hpf, gpia mRNA is strongly expressed in the retina of eye, tectum, hindbrain, and gut derivatives such as liver, intestine and circular smooth muscle layer of the swim bladder. By contrast, gpib is expressed in the yolk syncytial nuclei of late blastula, gastrula and segmentation embryos. Somitic gpib expression initiates in late pharyngula embryos, and it is most prominent in the muscle of hatching embryos around 48-60hpf. Transcript of gpib is also expressed in the pectoral fins and portions of the pharyngeal arches in the hatching period. The differential expression of gpia and gpib in zebrafish suggests partition or divergence of gpi functions between the two duplicates.

Aedes aegypti in Tahiti and Moorea (French Polynesia): isoenzyme differentiation in the mosquito population according to human population density.

Genetic differences at five polymorphic isoenzyme loci were analyzed by starch gel electrophoresis for 28 Aedes aegypti samples. Considerable (i.e., high Fst values) and significant (i.e., P values >10(-4)) geographic differences were found. Differences in Ae. aegypti genetic structure were related to human population densities and to particularities in mosquito ecotopes in both Tahiti and Moorea islands. In highly urbanized areas (i.e., the Papeete agglomeration), mosquitoes were highly structured. Recurrent extinction events consecutive to insecticidal treatments during dengue outbreaks tend to differentiate mosquito populations. In less populated zones (i.e., the east coast of Moorea and Tahiti), differences in ecotope characteristics could explain the lack of differentiation among mosquitoes from rural environments such as the east coast of Tahiti where natural breeding sites predominate. When the lowest populated zones such as Tahiti Iti and the west coast of Moorea are compared, mosquito are less differentiated in Moorea. These results will be discussed in relation to the recent findings of variation in mosquito infection rates for dengue-2 virus.

Nucleotide binding to autotaxin: crosslinking of bound substrate followed by lysC digestion identifies two labeled peptides.

Autotaxin (ATX) is a 125 kDa glycoprotein motility factor and exoenzyme which can catalyze the hydrolysis of either the alpha-beta or at the beta-gamma phosphodiester bond in ATP. Its motility stimulating activity requires an intact 5'-nucleotide phosphodiesterase (PDE) active site. Photolysis-dependent labeling of ATX with alpha-[32P]-8-N3-ATP, lysC digestion, and peptide HPLC resolved two radioactive fractions containing single peptides whose amino-terminal sequences were determined. Peptide A (T210FPNLYTLATG. . .) was derived from the PDE active site and peptide B (Y318GPFGPEMTNP. . .) was not previously known to be involved in any of the activities of ATX. The differential effect of NaCl concentration on the labeling of these two peptides, as well as on the two reaction types catalyzed by ATX, allows a classification of activities which predicts both the position of preferential peptide labeling by bound ATP and also the position of phosphodiester bond hydrolysis.

Drug sensitivity and isoenzyme type in cloned lines of Plasmodium falciparum.

Clones have been derived by limiting dilution from recent isolates of Plasmodium falciparum from Africa and Brazil. These clones have been characterized for pyrimethamine and chloroquine sensitivity and/or isoenzyme type. Clones obtained from an isolate containing a mixture of GPI isoenzyme types were found to have (with one exception) only GPI-1 or GPI-2. Clones differing 1,000-fold in pyrimethamine resistance were derived from a single isolate from Brazil which was resistant to both pyrimethamine and chloroquine. Several levels of chloroquine sensitivity were observed in the isolates studied. All clones showed levels of chloroquine sensitivity similar to that of their parent isolates. The KZ1 isolate from East Africa had an intermediate level of chloroquine resistance and a flat dose-response curve and each of its clones had a similar dose-response curve, indicating that the intermediate level of chloroquine resistance did not result from the KZ1 isolate's being a mixture of clones with high and low sensitivity.